const arr = [
  { name: "张三", age: 20 },
  { name: "李四", age: 22 },
  { name: "王五", age: 21 },
];

arr.forEach((item, index) => {
  console.log(index);
  console.log(item);
});

const findFirst = arr.find((item) => {
  return item.age > 20;
});

console.log("\n大于20岁", findFirst);

const findAll = arr.filter((item) => {
  return item.age > 20;
});

console.log("\n", findAll);

//映射:elmeA->elemB 生成新数组
//返回新的对象,且年龄都加1

const mapArr = arr.map(function (item) {
  // const newItem={};
  // newItem.name=item.name;
  // newItem.age=item.age+1;
  const newItem = { ...item, age: item.age + 1 };
  return newItem;
});

console.log(mapArr);
console.log(mapArr === arr);

//排序,不生成新数组
const sortArr=arr.sort((a, b) => {
  return a.age - b.age;
});esxXxxxxxxxxxxxxxxxxxx 
console.log(sortArr);
console.log(sortArr===arr);
